Stimulated Raman Scattering in Analytical Spectroscopy

Abstract Stimulated Raman scattering (SRS) was first observed by Woodbury and Ng [l] using a nitrobenzene Kerr shutter as the Q-switch of a ruby laser, and then identified by Eckhardt et al. [2]. If threshold requirements for the pump intensity and the interaction length were fulfilled for a given gain medium, SRS could be performed in a simple laser spectroscopy experiment of toluene, where a projected halo (or ring pattern) of blue-green light around the pump laser spot was observed on a card placed after a 5-cm-long cylindrical sample cell (see Fig. 1). A measurement of the radius of the halo as a function of distance along the pump beam path would determine its origin to be a point inside the sample cell, as shown in Fig. 2. However, the halo might disappear if a 1-cm-long cylindrical cell was substituted. Similar halos were observed for benzene over a wide range of pump laser wavelengths, from 445 to 535 nm for instance. The colors of the halos induced by different pump laser wavelengths would be slightly different.